White light emission of a predetermined chromaticity can be generated by innumerable spectral power distributions (known in the art as SPD), each of which can be particularly selected to provide lumen output or color rendition. Most fluorescent lamps as marketed today are designed to generate radiations of a "white" color as efficiently as possible to that the best possible light output will be achieved for a given wattage input, and the fixed spectral energy distribution of so-called halophosphate phosphor is generally used throughout the industry. Of course, for best color rendition of illuminated objects, the illumination should approximate that of daylight. In recent years, particularly for illumination in clothing and similar stores, more emphasis is being placed upon good color rendition of fabrics in order that the fabrics appear much the same in the store and in daylight. When fluorescent lamps are modified to improve the color rendition of objects illuminated thereby, usually by adding more blue and more red emission, the phosphors which emit in the shorter visible wavelengths and the longer visible wavelengths also normally generate substantial amounts of emission in the near ultraviolet and near infrared, respectively. This ultraviolet emission and infrared emission represents wasted energy, since it is invisible, which substantially decreases the luminous deficiency for such lamps for converting electrical energy to visible radiation.
The internationally accepted method for standardizing and measuring the color rendering properties of light sources is set forth in the publication of the International Commission on Illumination, identified as publication C.I.E. No. 13 (E-1.3.2.) 1965.